Various three dimensional plastic networks find utility in a wide variety of applications. For example, a three-dimensional web which may be formed of crimped staple fibers adhered together at points of contact or of extruded, autogenously bonded, continuous filaments. The webs may be employed as the structural element of a non-woven abrasive pad or article. Additionally, the same fiber or filament structures and other three-dimensional open plastic networks such as reticulated foams may be employed as filters, mats for cushioning, wiping, or any of a wide variety of other uses.
Various methods of making three-dimensional structures of various materials such as plastics are known in the art. U.S. Pat. No. 4,332,757 (Blackmon), discloses the preparation of a textured continuous filament yarn made by combining molten streams of polymer in a side-by-side configuration with one stream at a higher speed than the other to create a yarn with a false twist.
U.S. Pat. No. 4,384,022 (Fowler), assigned to the assignee of the present application, discloses a filamentary structure comprising a thermoplastic core filament extending in successive turns of spiral and thermoplastic sheath filaments which extent linearly generally in the direction of the axis along the outside of the spiral. The structure formed by this disclosure, however, cannot include a core filament having an aspect ratio much greater than one in order to maintain the spiral.
U.S. Pat. No. 3,178,328 (Tittmann) discloses a process and apparatus for producing a plastic net utilizing a die having an oscillating portion to extrude linear filaments, together with oscillating filaments to create a sine wave in the oscillating filaments, thereby creating a net-like structure. Tittmann's disclosure fails to indicate that anything other than a flat plastic net may be produced.
U.S. Pat. No. 3,193,604 (Mercer) teaches the ability to form an extruded sheet having ribs on both sides of the sheet by using a reciprocating or rotating extrusion die. The ribs on any given side may intersect or join each other depending on the rib spacing and the amplitude of the rib oscillation.
U.S. Pat. No. 4,233,259 (Pietratus) teaches the method of extrusion of a single inverted "T" (cross section) element or strand of which the upward leg undulates to form an untapered "wavy fin". The undulation is caused by having a shorter length of the approach surface leading to the fin profile opening in the die than that leading to the base opening. This causes areas of higher flow velocity which in turn results in an increased supply of the material to be extruded to these regions of the profile openings. The patent also teaches the need for a guide plate near the orifice exit to control width and/or change the direction of the fin folding.
U.S. Pat. No. 4,419,315 (Kessler) teaches the extrusion of a weatherstrip comprising a plurality of thin untapered flexible ribs in a wavy pattern that is attached to a backing strip from the same extrusion process. Straight and sinusoidal rib combinations are also disclosed. Kessler's disclosure fails to reveal ribs with non-uniform cross-sectional profiles.
U.S. Pat. No. 4,631,215 (Welygan), assigned to the assignee of the present application, discloses an extruded article comprising a plurality of linear spaced parallel extruded filaments separated by a regularly folded undulated extruded element having an aspect ratio of at least about two. The undulations have opposed apexes on either side thereof with apexes on one side of the undulated elements being bonded initially without adhesive to one of the parallel extruded elements and the apexes on the other side of the undulated element being bonded to the other parallel extruded element.